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Background Attack Aftermath Evidence Misinformation Analysis Memorial

Symmetry

The Demolition-Like Symmetry of the Twin Towers' Falls

This photograph shows the South Tower about five seconds into its "collapse" from the west. This was the less symmetrical of the two collapses.

Getting buildings to fall vertically (i.e.: symmetrically about their vertical axes) is what the art and science of controlled demolition are all about. By causing a building to fall vertically into its footprint, demolitions experts avoid damage to surrounding buildings. This is achieved through the careful placement and timing of explosives so as to cause the simultaneous and symmetric failures of all the main structural supports. Given the strength and resilience of steel, the failure to break even one of the major columns in a steel-framed building could cause it to tip to one side as it collapsed.

It is inconceivable that any random event or combination of events, such as aircraft collisions, fires, or fuel tank explosions, could cause the simultaneous failure of all the support columns in a building -- especially a tall steel-framed building -- needed to cause it to collapse vertically.

Both of the Twin Tower collapses exhibited remarkable symmetry. The North Tower's collapse commenced suddenly. The top of the tower seemed to effortlessly telescope down into the intact portion of the building. The collapse remained symmetrical from start to finish. The South Tower's collapse behavior was more complex. Its top first tipped for about two seconds, then started to descend. Despite the initial asymmetry of the collapse, it became more and more symmetric after the top started to fall. Once the top disappeared into the enormous dust cloud, there was no further evidence that the top had started to topple, except for a leaning anvil-shaped cloud of darker dust.

The centered collapses meant the falling mass followed the path of maximum resistance. That's the opposite of how we expect a structure to behave when it falls apart in any kind of natural process. Even if the towers were made out of clay, we wouldn't expect them to collapse in such a dead-centered fashion. It's all the more incredible that a steel structure would shred itself by falling into itself instead of falling over.

These photographs show the South Tower from the south at about two seconds and eight seconds after its top started to plunge downward. They show that the collapse became more symmetric as it progressed. Any natural collapse would have become less symmetric as it progressed.

There are many examples of steel-framed buildings undergoing unintentional collapses as a result of severe earthquakes. In contrast to the destruction of the Twin Towers, no such collapses have been vertical or total -- let alone explosive. Rather, steel-framed buildings destroyed by earthquakes have toppled.


page last modified: 2008-04-30